1. Field of the Invention
The present invention pertains to a system and method for filling a portable liquid oxygen (PLOX) unit, and, in particular, to such a system and method that automatically shuts off the flow of LOX to the PLOX unit and allows for “hands free” filling.
2. Description of the Related Art
The delivery of supplemental oxygen to a patient is typically prescribed for individuals suffering from pulmonary/respiratory problems. The prescription and delivery of supplemental oxygen is undertaken to ensure that sufficient oxygen levels are received by the patient. Situations where supplemental oxygen may be prescribed include individuals afflicted with a chronic obstructive pulmonary disease, such as asthma, as well as individuals suffering from diseased or damaged lungs.
It is known to deliver supplemental oxygen using a liquid oxygen (“LOX”) system. A conventional LOX system includes a large stationary LOX storage canister that is located at and remains at the user's home. The stationary LOX canister is replenished periodically from a mobile LOX storage vessel, which is typically a truck carrying a large quantity of LOX. A conventional LOX system also includes a small, portable delivery apparatus weighing from five to thirteen pounds that can be filled from the stationary unit for trips outside the home.
The portable delivery apparatus converts the liquid oxygen to a breathable gas for consumption by the user. These systems have limited utilization due to the low LOX capacity of the portable delivery apparatus and the administered LOX flow rate. Furthermore, even when not in use, the LOX within the portable delivery apparatus evaporates at a typical rate of one pound per day, empting the portable delivery apparatus LOX supply over time even if it is not used. Consequently, when using a portable LOX system, the user must return to the LOX supply to refill the portable delivery apparatus.
One such LOX system is disclosed in U.S. Pat. No. 6,742,517 (“the '517 patent”) entitled, High Efficiency Liquid Oxygen Storage and Delivery System. As disclosed in this patent, a typical LOX system includes a stationary LOX storage canister located in an individual's home and a portable LOX delivery unit that the patient uses outside the home. The stationary LOX storage canister must be periodically refilled with LOX by a distributor via a truck, van, or other vehicle capable of carrying a large quantity of liquid oxygen. The name of the portable delivery unit in the commercial implementation of this LOX system and described in the '517 patent is the HELiOS300. As identified at the HELiOS website, www.heliosoxygen.com, the HELiOS H300 portable LOX delivery unit has a limited capacity for storing liquid oxygen. This capacity is limited to eight to ten hours of usage, after which the LOX is depleted.
The HELiOS system is refilled by firmly forcing the HELiOS H300 portable LOX delivery unit onto the LOX storage canister by pressing down on the HELiOS H300 portable LOX delivery unit to cause it to engage with the LOX storage canister. While forcing the HELiOS H300 portable LOX delivery unit onto the LOX storage canister the user must manually move a vent valve level on the exterior of the portable deliver unit to an open position. This requires simultaneously applying a downward force on the HELIOS H300 portable LOX delivery unit and moving the valve level. Naturally, this requires using both hands or using more than one person to fill the portable delivery unit.
During filling, the user must maintain a watch on the HELiOS H300 portable LOX delivery unit until sputtering in the filling noise associated with the filling of the unit. In addition, the user must watch for the release of white vapor from the HELiOS H300 portable LOX delivery unit in order to ensure that the unit has been completely filled. After which, the user is instructed to release the portable LOX delivery unit from the storage canister.
In another system, such as the Stroller/Spirit sold by Caire, Inc., the portable LOX delivery unit can be attached to the LOX storage canister. However, the user must still maintain a vigil over the portable LOX delivery unit to determine when the unit has been filled. Again, this requires that the user discern a change in the sound associated with the filling of the unit and visually notice a white cloud being released by the unit.
It can be appreciated that conventional processes for filling a portable liquid oxygen system have two main problems. Firstly, they are quite cumbersome and difficult for most users. Many systems, such as process for filling the HELiOS H300 portable LOX delivery unit, require the users to use one or both hands to fill the system, which can be quite difficult for them to accomplish. This is especially true for users with limited strength or dexterity. Secondly, they require the user to determine when the system is full based on sound changes and/or white clouds of oxygen gas and small amounts of liquid venting from the system. This type of filling process is ambiguous at best for the user to know whether the system has actually been filled to the appropriate liquid level. If the user is audibly and/or visually impaired, the process can be quite problematic for the user.